In many plans, that means rather than paying a $15 or $30 co-pay as a patient would when he or she goes to a primary care doctor, the patient would be responsible for a co-pay that could range up to $50 or more.

His bill would prohibit insurers, other than the state's own employee health plan, from charging larger co-pays than for physicians if a medically similar service is provided. A similar measure was filed two years ago after a legislative study committee suggested it, although it did not make it all the way through the legislative process.

As Burr and others spoke about and made changes to the bill, the specter of a decade-old scandal loomed, unacknowledged, over the proceedings until Rep. Gary Pendleton, R-Wake, stood up to offer an amendment and recalled another time House members took up the chiropractic co-pay issue.

"This body did this when Jim Black was speaker. It was negotiated outside of Wake County, you may remember," Pendleton said.

Black was a Mecklenburg County Democrat who served as House speaker from 1999 through 2006. In 2005, he slipped a very similar provision into the state House budget, using his prerogative as one of the chamber's most powerful members.

Two years later, Black pleaded guilty in federal court to accepting $25,000 in cash given to him by three chiropractors between 2002 and 2005. That money was handed over to him in restaurant bathrooms, and he used it to help political allies, who in turn helped Black hold on to power. He spent roughly three years in prison and paid a hefty fine as a result.

The fallout from the Black scandal prompted sweeping ethics reforms, and lawmakers quickly undid the provision he inserted as part of the quid pro quo.

Still, the chiropractic industry has remained a vocal force in North Carolina politics. Political action committees and individuals associated with the industry made 105 contributions, totaling $44,200, to various state House and Senate candidates during 2013 and 2014, according to State Board of Elections data made searchable by the National Institute on Money in State Politics. Another $9,000 went from the state chiropractic association's PAC to Republican Party organs, the data shows.

"This really is a journey that began in 2009 when the chiropractors came and asked for co-pay parity," Joe Siragusa, a chiropractor who serves as executive director of the North Carolina Chiropractic Association, told the House Insurance Committee earlier this week.

He pointed to studies done over the past three years that show allowing for more chiropractic care saves money in the long run.

"All we are asking is that patients have a choice if they wake up in the morning and they want to go to their chiropractor, that they don't have a financial disincentive," Siragusa said, adding that chiropractors should be considered primary care doctors for a narrow scope of problems.

The bill, which cleared the House at 11:39 p.m., now goes to the state Senate for consideration.